This study focuses on the role of early childhood inhibition in the development of pathological risk indicators in children of families with and without parental depression. Patterns of child behavior in the face of the unfamiliar (persons, places) such as behaviors expressing inhibited exploratory activity and social withdrawal are observed at 2 to 3 years of age in semi-naturalistic but standard settings, which represent varied contexts of unfamiliarity. Analyses of these data revealed that five reliable dimensions of response styles could be empirically derived from our observation coding system. These dimensions meaningfully distinguish groups of children in our sample at the very young age. Comparisons of these five dimensions of early behavioral inhibition across maternal diagnostic groups (normal, major depressive and bipolar) indicate that the young children of the major depressive and bipolar) indicate that the young children of the major depressive mothers typically exhibit the most inhibited forms of exploratory behavior, a strong tendency to cling to mother in novel situations, and characteristically flat and withdrawn displays of affect. Children of the bipolar mothers typically exhibit the most active and independent forms of explorations of novel environments. In a situation of an unfamiliar person, these children score at both the inhibited and uninhibited polar extremes. However, in this situation, these children of bipolar mothers do not demonstrate a clinging dependency on mother and typically present positive displays of affect. Observational data relating to mothers' behaviors that are concurrent with child behaviors in these situations are being analyzed to examine the ways in which mothers in these groups function to facilitate or hinder the child's exploration and approach of unfamiliar situations.